1. Field of the Invention
The present invention relates generally to copiers, printers and other image printers that produce images by using a photosensitive transfer type development heat material, and more particularly it relates to development heat and transfer pressure devices that develop exposed images by heat and transfer the developed images to paper using pressure.
2. Description of the Prior Art
There are many methods and devices in use for printing images on paper, the ubiquitous xerographic-based office copier and laserprinter being prime examples in the United States. A prior art example of an image printer that uses a photosensitive transfer type development heat material is disclosed in Japanese Laid-Open Patent Publication 62-147461. These types use an intermediate medium that is photosensitive and can print a copy of the image that was focused on it by transferring the image to paper under both heat and pressure. Inks exist in microcapsules held on with a binder to the medium. See, U.S. Pat. No. 4,399,209. A plain pressure roller is used in some that have separate transfer pressure and heating. A uniform and sufficient pressure over an entire image area usually requires sandwiching the image mediums between rigid rollers. Metal pressure rollers are therefore usually used. Japanese Laid-Open Patent Publication 62-232653 discloses that a compact device can be made by adding a heating device to a transfer pressure device which also allows a reduction in the necessary pressure.
The prior art has some significant problems. First, since development heat and transfer pressure mechanisms are separate, and maintained at independent temperatures. This adds cost and complexity. In the cases where the two mechanisms are adjacent to one another, each is affected by the temperature of the other. Time is needed to stabilize the two, and this introduces delays. Outside environment changes can also upset the temperature control, and image quality will suffer as a result. Second, since there are two heating mechanisms, so a large number of parts is needed to independently and accurately control the temperatures of both, thus making the printer surprisingly large and the control circuits complicated.
In the prior art, there is often no heater for transfer pressure or heaters for developing and transfer pressure were independent of each other. High transfer pressure temperatures were not tried, since that would make the device more complicated and would increase costs.
A low cost image printer that is compact, lightweight, and can simply and consistently produce high quality images is needed.